We know there are challenges in trying to obtain biopsies, especially when you’ve already been diagnosed and had treatment, and then the tumor stops responding to the therapy that’s given. We like to do repeat biopsies because we know that the tumor can change over time, after being exposed to different types of therapies. That can sometimes be challenging, and add some risk to patients because it is an invasive procedure — many times we use a needle that will go through the chest, into the tumor, to try and extract enough tissue to make these measurements. Emerging technology that has really been very popular the last few years has been trying to utilize your blood to measure these markers. You’ll hear terminologies like circulating tumor cells, or CTCs, circulating DNA — a lot of different things that are measuring, trying to identify things in your blood that may be representative of your tumor in your chest, or your liver, or where it may be.
One of the technologies is called circulating tumor cells — in this, you are actually trying to isolate these cancer cells in the blood. Some of the technologies are cell search systems, in which you isolate, what we call, through a filter, these tumor cells — that is a bit challenging, it has been inconsistent with some of the results. Also, circulating cell-free DNA is another technology — this, again, is trying to measure small pieces of DNA that are shed from the tumor, and it’s a little easier to pick up that, as opposed to actual, whole cancer cells, in the bloodstream.
There are some commercial tests out there — Guardant360 is one of them, that’s based, again, on the technologies discussed in the NGS section, that would be next-gen sequencing, and also OncoBEAM or Sysmex Inostics — these are also commercial tests, and I can tell you there are many more that are coming. Right now, I would not view them, necessarily, as your first choice, over getting a tumor biopsy. However, a lot of the quality analytics that have been done have shown that they can measure almost as accurately in the bloodstream, using these technologies, as one would taking tumor tissue through a procedure, using an interventional procedure like a bronchoscopy or interventional radiology.